1. Field of the Invention
The present invention relates to a manufacturing method for a thermal head.
2. Description of the Related Art
There have been conventionally known a thermal head which is used in a thermal printer often mounted to a portable information equipment terminal typified by a compact hand-held terminal, and which is used to perform printing on a thermal recording medium based on printing data with the aid of selective driving of a plurality of heating elements (for example, see JP 2007-320197 A).
In terms of an increase in efficiency of the thermal head, there is a method of forming a heat insulating layer below a heating portion of a heating resistor. By formation of the heat insulating layer below the heating portion, of an amount of heat generated on the heating resistor, an amount of upper-transferred heat which is transferred to an abrasion resistance layer formed above the heating portion becomes larger than an amount of lower-transferred heat which is transferred to a heat storage layer formed below the heating portion, and hence energy efficiency required during printing can be sufficiently obtained. In the thermal head described in JP 2007-320197 A, a hollow portion is provided between a substrate and a supporting plate which are integrated with each other, and this hollow portion functions as a hollow heat insulating layer. Thus, the amount of upper-transferred heat becomes larger than the amount of lower-transferred heat, and the energy efficiency is increased.
In the manufacturing method for the thermal head described in JP 2007-320197 A, a gap portion is formed inside a protrusion which is formed on one surface of the substrate, and the flat supporting plate is fused and bonded onto the other surface thereof to enclose the gap portion, whereby the hollow portion is formed. In this manufacturing method, there is a risk that the substrate breaks because the hollow portion is formed before the substrate is reinforced by the supporting plate, and there is a problem that it is difficult to handle the substrate during a manufacturing process. Further, an original thickness of each of the substrates varies, and hence there is a problem that it is difficult to control the thickness of the substrate serving as the heat storage layer above the hollow portion.